Fix potentially invalid macro name in generated version header (#38)

* Fix potentially invalid macro name in generated version header

The generated name was invalid if the target name contained characters
that are not legal in macro identifiers. This commit replaces all
illegal characters with the underscore "_".

* Update CMakeLists.txt

---------

Co-authored-by: Lars Melchior <TheLartians@users.noreply.github.com>

Author: jan-moeller

CMakeLists.txt

@@ -81,6 +81,8 @@ function(packageProject)
       endif()
 
       string(TOUPPER ${PROJECT_NAME} UPPERCASE_PROJECT_NAME)
+      # ensure that the generated macro does not include invalid characters
+      string(REGEX REPLACE [^a-zA-Z0-9] _ UPPERCASE_PROJECT_NAME ${UPPERCASE_PROJECT_NAME})
       configure_file(
         ${PACKAGE_PROJECT_ROOT_PATH}/version.h.in
         ${PROJECT_VERSION_INCLUDE_DIR}/${PROJECT_VERSION_HEADER} @ONLY